We wish to share our experience with three cases of quadrigeminal cistern lipomas, all of whom were discovered incidentally during computed tomography/magnetic resonance imaging (CT/MRI) examination of patients for related or unrelated conditions.

The first case, a 31-year-old male, presented with a history of minor head injury with no loss of consciousness, convulsions or vomiting. A noncontrast cranial CT study was performed which revealed a fat attenuation lesion on the left side of the quadrigeminal cistern [Figure 1]. No other intracranial pathology was detected.

Figure 1: (a and b) Axial computed tomography scan shows a fat attenuation lesion in the left quadrigeminal cistern suggestive of a lipoma

The second case, a 36-year-old male, presented with recurrent headache and dizziness. His neurological and systemic examination did not reveal any abnormality. A noncontrast cranial CT showed a sharply delineated fat attenuation lesion within the quadrigeminal plate and extending into the cistern on the right side with focal cisternal widening [Figure 2]a and b. An MRI study confirmed the presence of a focal lesion within the quadrigeminal cistern. The lesion demonstrated marked hyperintensity on T1-weighted (T1W) images with relatively less hyperintensity on T2-weighted (T2W) images with suppression of signal on short T1 inversion recovery (STIR) sequence confirming the fatty nature of the lesion [Figure 2]c-f. No other intracranial abnormality was noted.

The third case, a 42-year-old female, presented with recurrent episodes of severe headache of 4 months duration and being previously treated with the clinical diagnosis of migraine. Her general and neurological examination was normal. An MRI of the brain was performed which showed a small focus of fat signal intensity within the quadrigeminal cistern. The lesion was hyperintense on T1W images, with relatively less hyperintensity on T2W and fluid-attenuated inversion recovery images, with no mass effect or ventricular dilatation [Figure 3]a-c. No other abnormal findings were noted.

Figure 2: (a and b) Axial computed tomography scan shows a lipoma in the right quadrigeminal cistern; unenhanced axial (c and d) and sagittal (e) T1-weighted magnetic resonance images show a hyperintense lesion within the quadrigeminal cistern. The lesion is relatively less hyperintense on T2-weighted image (d) and is suppressed on short T1 inversion recovery image (f) thereby confirming the fatty nature of the lesion

Figure 3: (a-c) Magnetic resonance imaging of the brain with axial T1- weighted (a), T2-weighted (b) and fluid-attenuated inversion recovery (c) images showing a small lesion which is hyperintense on all sequences within the left quadrigeminal cistern suggestive of a lipoma

All the three patients did not require any surgical intervention and were managed conservatively. They are on a regular follow-up.

Intracranial lipomas are neither tumors nor hamartomas. They represent developmental anomalies resulting from abnormal differentiation of embryologic meninx primitiva (the mesenchymal anlage of the meninges) during the development of the subarachnoid cisterns. The relative frequency of the various locations of the lipomas correspond to the temporal sequence of dissolution of the meninx primitiva. The lipomas are frequently associated with abnormal development and hypoplasia of adjacent structures such as the corpus callosum, vermis, and inferior colliculi. [1]

Quadrigeminal cistern lipomas account for approximately 10-25% of all intracranial lipomas. Generally asymptomatic, these are detected incidentally at imaging, and have a fairly diagnostic imaging characteristics on CT or MRI. Hence, histopathologic confirmation is practically never required. The larger lesions may, however, present with symptoms resulting from compression of the adjacent brain parenchyma, cranial nerves, vessels or with an obstructive hydrocephalus. [2],[3]

The imaging features of quadrigeminal cistern lipomas are quite characteristic and the fatty nature of the lesion can be confidently established by its typical low attenuation values (−20 to −80 HU) on CT and the short T1 and T2 sequences on MRI. Fat suppression MRI sequences like STIR are useful for confirming the fatty nature of the lipoma. [4]

Small quadrigeminal lipomas generally do not require surgery because these tumors rarely reach a size sufficient to cause mass effect or intracranial hypertension. Surgical removal is also discouraged due to the dense vasculature of the lipoma and its tendency to adhere to the surrounding neural tissue making resection technically difficult. [5] If the lesion progresses in size and causes ventricular obstruction and symptoms of raised intracranial pressure or compression of adjacent neural structures occur, surgical intervention is indicated.